Urea Dosing Calibration Procedure – OEM-Agnostic Protocol

The OEM-agnostic urea dosing calibration procedure decouples dosing optimization from proprietary ECU firmware by treating the SCR system as a black-box process with measurable inputs (engine load, speed, exhaust temperature, NOₓ concentration) and outputs (downstream NOₓ, NH₃ slip, catalyst temperature). Calibration begins with steady-state engine dynamometer testing across a representative grid of operating points (e.g., 10–100% load, 1000–2500 rpm), where raw exhaust NOₓ is measured upstream of the SCR, and post-SCR NOₓ and NH₃ are quantified using certified chemiluminescence (CLD) and tunable diode laser (TDLAS) analyzers. A dosing map—expressed as urea mass flow rate per unit of engine NOₓ mass flow—is iteratively refined to maximize NOₓ conversion (>90%) while maintaining NH₃ slip <10 ppm at all validated points. Critical enablers include exhaust gas recirculation (EGR) stability verification, catalyst light-off state confirmation via thermocouple arrays, and correction for urea decomposition inefficiency (typically 70–85% hydrolysis yield under transient conditions). The resulting calibration table can be implemented via generic CAN-based dosing controllers or mapped into after-market ECU tuning platforms, enabling cross-platform validation, regulatory audit readiness, and fleet-wide retrofit compatibility without OEM toolchain dependencies.